For hypertension (high blood pressure) the maximum benefit of diltiazem usually occurs after 14 days. However, diltiazem does not cure high blood pressure; it only helps to control it. If you are taking diltiazem to manage high blood pressure (hypertension), you must keep taking it as your doctor prescribes. If you stop taking the medication, your hypertension will be uncontrolled, which can lead to heart and blood vessel disease, kidney disease or stroke.It may take up to two weeks before you have less chest pain if you are taking diltiazem for angina. If you continue to experience chest pain after two weeks, talk to your doctor about adjusting the dose or switching to another medication. If your symptoms improve, don’t stop taking diltiazem or your chest pain will return.